President Biden visited Buffalo, New York, Tuesday, three days after an 18-year-old white supremacist shot dead 10 people at a supermarket in a predominantly Black neighborhood. Biden denounced the attack as an act of domestic terrorism and described white supremacy as a poison.

President Joe Biden: “Look, we’ve seen the mass shootings in Charleston, South Carolina; El Paso, Texas; in Pittsburgh; last year in Atlanta; this week in Dallas, Texas; and now in Buffalo — in Buffalo, New York. White supremacy is a poison. It’s a poison running through — it really is.”

Biden’s trip to Buffalo comes as more details emerge about how the gunman spent months plotting to carry out the mass shooting. Multiple news outlets are reporting the gunman used the online platform Discord to share details about his plot with a small group of people about 30 minutes before the massacre. No one who saw the messages is known to have alerted law enforcement to the imminent attack.